Fuel pumping apparatus

ABSTRACT

A fuel pump for supplying fuel to an engine includes a rotary drive shaft (12) having an enlarged portion (18) through which the rotary part of the pump is driven. The pump also has an annular cam ring (17) which is angularly adjustable within the pump housing to vary the timing of fuel delivery. The pump includes a transducer (31) having pole pieces (33, 34) which are located in close proximity to the elongated portion (18) of the drive shaft. The pole pieces form part of a magnetic circuit including a magnet and the pole piece (33) and the adjacent surface or the portion (18) are shaped so that the flux in the magnetic circuit varies in a cyclic manner as the shaft rotates. The pole pieces and magnet are mounted on the cam ring (17) and the transducer includes a former (37) carried by the housing of the pump and upon which is wound a winding. The former surrounds a part of the magnetic circuit and the former and the part of the magnetic circuit are shaped so as to allow angular movement of the cam ring.

This invention relates to a fuel injection pumping apparatus forsupplying fuel to an internal combustion engine the apparatus being ofthe kind comprising a housing, a cam actuated pumping plunger slidablein a bore, means for distributing fuel discharged from the bore duringsuccessive inward movements of the plunger, to a plurality of outletports in turn, a plunger actuating mechanism comprising a first partwhich is mounted for rotation in the housing and which in use is drivenin timed relationship with an associated engine to actuate the plunger,and a second part mounted in the housing and being angularly adjustabletherein about the axis of rotation of the first part, to enable thetiming of inward movement of the plunger to be varied and a transducermounted on said second part and responsive to indicia on said firstpart.

An apparatus of the aforesaid kind is shown in GB-A-2086491 in which thefirst part carries cam followers located at the outer ends respectivelyof pumping plungers and the second part is a cam ring having cam lobeson its internal surface which are engaged by the cam followers. Thetransducer is carried by the cam ring and is of the variable reluctancetype and is responsive to the passage of grooves which are formed in thesurface of the first part. The transducer since it is mounted on the camring moves in the use of the apparatus about the axis of rotation of thefirst part as the timing of fuel delivery is adjusted. As a result it isnecessary to provide a flexible connection to the transducer such aconnection in practice extending between the transducer and a connectorblock mounted on the housing. The provision of the flexible connectionpresents practical difficulties and the object of the invention is toprovide an apparatus of the kind specified in a simple and convenientform.

According to the invention in an apparatus of the kind specified thetransducer comprises first and second pole components and a magnetacting to polarize said components to opposite magnetic polarity, themagnet and said components being mounted on said second part and forminga magnetic circuit with said first part, said first part and one of saidcomponents being shaped so that the flux flow in said magnetic circuitvaries in a cyclic manner as the first part rotates in use, and asensing coil mounted on the housing of the apparatus and surrounding aportion of the magnetic circuit to provide the output signal of thetransducer.

An example of a fuel pumping apparatus in accordance with the inventionwill now be described with reference to the accompanying drawings inwhich:

FIG. 1 is a diagrammatic sectional side elevation of a pumping apparatusgenerally of a known type,

FIG. 2 is an end view with parts removed, showing a modified transducerin accordance with the invention,

FIG. 3 is a perspective view with parts removed, showing the transducerof FIG. 2,

FIG. 4 shows a sectional side elevation of another example of thetransducer,

FIG. 5 shows an exploded perspective view of the transducer of FIG. 4,

FIG. 6 shows in diagrammatic form a side elevation of a further exampleof the transducer, and

FIG. 7 shows a plan view of part of the transducer of FIG. 6.

Referring to FIG. 1 of the drawings the apparatus comprises a multi-parthousing 10 in which is journalled a rotary cylindrical distributormember 11 which is coupled to so as to rotate with, a drive shaft 12extending from the housing and arranged in use to be driven in timedrelationship with the associated engine.

Formed in the distributor member is a transverse bore 13 in which ismounted a pair of pumping plungers 14. At their outer ends the plungersengage shoes 15 respectively which in turn carry rollers 16, the rollersand shoes constituting cam followers for engagement with the internalperipheral surface of a cam ring 17 mounted for angular adjustmentwithin the housing.

Formed on the cam ring are a plurality of equi-angularly spaced camlobes (not shown) and the cam followers are mounted in radially disposedslots which are formed in an enlarged portion 18 of the drive shaftwhich surrounds the distributor member.

Communicating with the bore 13 is a longitudinal passage 19 which inturn communicates with an outwardly extending delivery passage 20 whichis arranged to register in turn as the distributor member rotates, witha plurality of outlet ports 21 which in use are connected to theinjection nozzles of the associated engine. Also communicating with thepassage 19 is a plurality of radially disposed inlet passages 22 andthese can register in turn with an inlet port 22A which is formed in thehousing 10 and which is in communication with the outlet of a source 22Bof fuel under pressure. The pressure of fuel delivered by the source isarranged to vary in accordance with the speed at which the apparatus isdriven.

The inlet ports 22 can also communicate in turn with a spill port 23such communication being established during the time when the deliverypassage 20 is in communication with an outlet port 21. The flow of fuelthrough the spill port 23 is controlled by an electrically operatedspill control valve 24 the operation of which is controlled by anelectrical control system 24A.

In operation, when the rollers 16 of the cam followers engage theleading flanks of the cam lobes, fuel will be displaced from the bore 13and will flow through the delivery passage to an outlet port 21. Fuelwill only be displaced to the outlet port providing the spill controlvalve 24 is closed and hence this valve is used to determine thequantity of fuel which is supplied by the apparatus to the associatedengine at each injection stroke. As the distributor member rotates, thedelivery passage 20 moves out of register with the outlet port 21 and aninlet passage 22 moves into register with the inlet port 22A. Fuel istherefore supplied to the bore 13 to effect full outward movement of theplungers 14 and the associated cam followers, as permitted by the camlobes or by stop plates not shown. During continued rotation of thedistributor member the inlet passage 22 is moved out of register withthe inlet port 22A and the delivery passage 20 moves into register withthe next outlet port 21 so that fuel is supplied to the outlet ports inturn during successive inward movements of the pumping plungers.

The timing of delivery of fuel is varied by moving the cam ring 17angularly within the housing and this is effected in known manner bymeans of a fluid pressure operable piston 25 which is housed within acylinder and which is spring biased in the retard direction. Fuel can beadmitted to the cylinder directly from the source 22B or alternativelyand as shown, an electrically operated valve 26 is provided and this iscontrolled by the control system 24A.

The control system 24A in order that it can control the operation of thespill control valve 24 needs to be supplied with signals indicative ofthe speed of the associated engine and also the position of thedistributor member relative to the cam ring 17. A first transducer 27 ofthe variable reluctance type is provided and this is fixed to thehousing and senses the passage of indicia 28 formed on the enlargedportion 18 of the drive shaft. In FIG. 1 the indicia are in the form ofgrooves cut into the periphery of the drive shaft at equally spacedintervals about the drive shaft. A further transducer 29 is provided andthis is attached to the cam ring 17 and is also of the variablereluctance type. The transducer 29 is also responsive to the passage ofthe indicia 28. A disadvantage with the arrangement shown in FIG. 1 isthat a flexible lead must be provided between the transducer 29 and aconnector block which is not shown, mounted on the housing.

In order to overcome the problem of the flexible lead the transducer 29is replaced by the arrangement which is shown in FIGS. 2 and 3 andreferring to these Figures there is illustrated to enlarged scale, theenlarged portion of the drive shaft 18 and in this example the peripheryof the drive shaft is provided with a plurality of teeth 30. Thetransducer which is generally indicated at 31 comprises a first polecomponent 32 in the form of an elongated arcuate member which is formedfrom magnetisable material and which at one end is provided with a poletip 33 which extends into close proximity to the pole teeth 30. The poletip as shown has a circumferential length corresponding to that of onetooth but it may define a number of teeth. The transducer also includesa second pole component in the form of a side plate 34 which is alsoformed from magnetisable material and which has an inner arcuate surface35 which is located against with a small clearance, a plane cylindricalportion of the drive shaft. Interposed between the plate 34 and themember 32 is a permanent magnet 36. As the drive shaft rotates, themagnetic flux in the member 32 will vary as the teeth 30 pass the poletip 33.

As shown in FIG. 2, a sensing coil 37 also forms part of the transducerand is located about the component 32. The sensing coil is wound upon aformer which is supported by means of a bracket 38 on the housing of theapparatus. The opening in the former is shaped so that there is nocontact between the component 32 and the former. The winding of the coilis connected by means of a lead to the aforesaid connector block andsince the coil is fixed relative to the housing, the lead does not haveto be constructed so as to accommodate movement. Also as shown in FIG.2, the component 32 extends between and is secured to the ends of asplit ring 39 which is secured to the cam ring 17 and which is formedfrom non-magnetic material.

The apparatus as described is of the type in which a distinct pair ormore of pumping plungers is provided in a bore in the distributormember. The construction of transducer however is equally applicable torotary distributor pumps of the type wherein the distributor memberforms the pumping plunger and is therefore moved axially to achieve thepumping action and is rotated to effect distribution of the pumped fuelto the outlet ports. In such an arrangement the distributor member or apart connected thereto is provided with a face type cam ring which isengaged by rollers mounted in a carrier fixed axially within thehousing. The carrier is angularly moveable to vary the timing of fueldelivery. In applying the construction of transducer to this type ofpump, the component 32 together with the magnet and plate, would bemounted on the aforesaid carrier, and the sensing coil would be mountedon the housing. The plate 34 and the component 32 would be located inclose proximity to a drive shaft of the apparatus.

With reference to FIGS. 4 and 5 the transducer comprises first andsecond annular pole components 40, 41 which are spaced by an annularpermanent magnet 42. The component 40 has teeth formed on its internalsurface corresponding to the teeth 30 on the drive shaft 18 and thecomponent 41 has its inner surface running in close proximity to thesurface of a plane portion of the drive shaft. The components 40, 41 andthe magnet are apertured as shown in FIG. 5, to receive screws whichhold the parts in assembly and to the cam ring.

The internal diameter of the magnet is large enough to accommodate anannular winding carried on an annular former 43 which is provided withoutwardly extending lugs 44. The lugs enable the former to be mounted inthe housing of the apparatus and one of the lugs carries the endconnections of the coil to the aforesaid terminal block. The lugs 44extend with clearance through slots 45 formed in one face of the magnet42, the slots being of a circumferential length long enough to allow forthe angular movement of the cam ring. The magnetic circuit of thetransducer includes the drive shaft 18 about which the coil and formerare located and as the drive shaft rotates cyclic variation of themagnetic flux flowing in the magnetic circuit takes place and a voltageis induced in the winding.

A further example is seen in FIGS. 6 and 7 and with reference to thesefigures, the drive shaft is shown at 18 and is provided with teeth 30.Also provided is a coil former 47 which is mounted on the housing of thepump by means of a bracket 46. The coil former is elongated in thedirection of shaft rotation and formed in the former is an elongatedslot 48. The former carries a winding 49 which is connected to theterminal block.

Extending in a generally radial direction through the slot 48 is a polepiece 50 which forms one of the pole components of the transducer andassociated with the pole piece is a permanent magnet 51, the magnet andthe pole piece being mounted on the cam ring so as to move angularlytherewith. The pole piece is polarized by the magnet and the flux in thepole piece varies as the teeth 30 move adjacent to its tip. The slot 48allows for movement of the pole piece 50 with movement of the cam ringabout the axis of rotation of the drive shaft. In this case the face ofthe magnet remote from the pole piece forms the other pole component ofthe transducer which carries the return flux, the actual return fluxpath incorporating a substantial air gap.

I claim:
 1. A fuel injection pumping apparatus for supplying fuel to aninternal combustion engine comprising a housing (10) a cam actuatedpumping plunger (14) slidable in a bore, means (11) for distributingfuel discharged from the bore during successive inward movement of theplunger to a plurality of outlet ports (21) in turn, a plunger actuatingmechanism comprising a first part (18) which is mounted for rotation inthe housing and which in use is driven in timed relationship with anassociated engine to actuate the plungers, and a second part (17)mounted in the housing and being angularly adjustable therein about theaxis of rotation of the first part to enable the timing of inwardmovement of the plunger to be varied and a transducer mounted on saidsecond part and responsive to indicia on said first part characterisedin that the transducer comprises first and second pole components (33,34, 40, 41, 50), a magnet (36, 42, 51) acting to polarize saidcomponents to opposite magnetic polarity, the magnet and said componentsbeing mounted on said second part (17) and forming a magnetic circuitwith said first part, said first part (18) and the one (33, 40, 50) ofsaid components being shaped so that the flux flow in said magneticcircuit varies in a cyclic manner as the first part rotates in use, anda sensing coil (37, 43, 49) mounted on the housing (10) of the apparatusand surrounding a portion of the magnetic circuit to provide the outputsignal of the transducer.
 2. An apparatus according to claim 1, in whichsaid portion of the magnetic circuit comprises an arcuate member (32)which extends between the magnet (36) and said one (33) of saidcomponents, said arcuate member extending in the direction of rotationof said first part (18).
 3. An apparatus according to claim 2, in whichthe opposite ends of said arcuate member (32) are secured to the ends ofa split ring (39) formed from non-magnetic material.
 4. An apparatusaccording to claim 3, in which said split ring (39) is adapted to besecured to said second part.
 5. An apparatus according to claim 2, inwhich the other (34) of said components comprises a plate (34) having asurface which lies in close proximity to a surface of said first part(18).
 6. An apparatus according to claim 1, in which said first andsecond components are defined by annular members (40, 41) and saidmagnet (42) is of annular form and is located between said members, saidmembers and said magnet being located about said first part (18), saidsensing coil being mounted on an annular former (43) located betweensaid annular members (40, 41) and within said magnet.
 7. An apparatus asclaimed in claim 6, in which said former (43) is provided with outwardlyextending lugs (44) which extend with clearance through slots (45)formed in the magnet (42) said lugs being utilised to secure the formerto the housing (10).
 8. An apparatus as claimed in claim 1, in whichsaid one (50) of said components extends in a radial direction and saidsensing coil (49) is wound upon a former (47) which is of elongated formin the direction of rotation of said first part (18), the formerdefining an elongated slot (48) through which said one of saidcomponents extends.
 9. An apparatus as claimed in claim 1, in which saidfirst part (18) is provided with a plurality of teeth (30) which definesaid indicia, about its periphery.